Surgically produced congenital diaphragmatic hernia in fetal lambs results in pulmonary hypoplasia and respiratory distress. This project is intended to investigate: 1) The pathogenesis of pulmonary hypoplasia in the lamb with diaphragmatic hernia; 2) The ventilatory and hemodynamic changes due to the hernia; 3) Methods of mechanical ventilatory support in the situation where parenchymal and mechanical respiratory defects are combined.